Friction spring unit



Oct. 7, 1947. I H. E. YTUCKER FRICTION SPRING UNIT Filed March 10, 1943w 1" .3 INVENTOR. fi'ulnll'm'zan Patented Oct. 7, 1947 Herbert E.Tucker, Chicago, I-ll.,-;assignor to .James R. Cardwell, .Chica'gmllLApplication March-10, 1943, -Serial No. 478,615

'8 Claims.

This invention relates toirailway cars, and more particularly tocushioning devices 'for rail-- way truck bolsters and'the like.

One of the objects of the invention is ithefprovision of anew andimproved .friction spring unit providing for substantiallyconstant'ffrictional resistance at alldegrees of compression of thespring unit and so designed that the magnitude of. the substantiallyconstant frictional :resistance may be set at various values.

Another object of the invention is the provision of a new and improvedfriction spring unit adapted to be used in a spring assembly forpreventing harmonic action of the assembly.

A further object of the invention is the provision of a newand improvedbolster spring having parts that frictionally resist both compressionand extension, and so constructed that its capacity maybe enlargedorreduced with 'a minimum of time and expense. A still further object ofthe invention is the provision of a new and improved spring frictionunit that is simple in construction, easily assembled, that isinexpensive to manufacture, and one in which its capacity may be easily:and readily increased or reduced at a minimum of time and expense.

Other and further objects and advantages of the invention will appearfrom the following description taken in connection withthe accom-'panying drawing, in which Fig. l is a side elevation of a portion of arailway truck,- showing the invention in position therein;

Fig. 2 is a top plan view of the friction spring unit;

Fig. 3 is a vertical section thereof; and

Fig. 4 is a perspective view of one of the friction sleeves.

Referring now to the drawing, the reference character indicates a truckwith parts broken away, having a side frame H provided with a bolsteropening [2 into which the end "of the bolster I 3 is adapted to extend,as is usualin such constructions. The bolster is adaptedto be supportedby a spring assembly l4; comprising the conventional bolster springs andone or more friction spring units 16, as will presently appear. Sincethe detail construction of the side frame, the bolster, and the bolstersprings 15 is conventional itis not thought necessary'to furtherillustrate or describe the same.

The friction spring unit 16 consists of a pair of chambered followers I1and I8, which 'are duplicates of each other and each of which com- 2prises :"a, hollow portion l'9, preferably cylindrical and havingatit-souter-end a radially extending flange'ZI against which is adapted"to be seated a spring :22 surrounding the cylindrical portions H), as"clearly indicated in Fig. 3 of the drawing. The cylindrical portion i9of each follower is preferably, though not necessarily, provided with acylindrical interior friction wall 23 forming a friction "surface whichis adapted to be frictionally engaged by 'a' friction member 24 forassisting in resisting the compression of the unit. The interior walloithe cylindrical portion of each follower is enlarged in diameter at itsouter end. as at 25, .to .form the shoulders 26, 21, on the followers.

Suitable means are provided for irictionally engaging theirictionsurfaces 23 of the followers, and, in the form 'of construction shown, afriction member '24 is employed for this purpose. This friction memberis in the form of a split sleever28, which is so constructed that it isnormally "of larger diameter than the interior of the diameter of thecorresponding chamber, so that it must be compressedin'order to insertthe same into said chamber when the sleeve is in position within thecylinder. The sleeve is flanged at its ends, or 't'he'exte-rnal'diameter of the intermediate portion of the sleeve 28 is reduced so asto form the flanges or shoulders 29 and 3| which are adapted to engagethe shoulders 26. 21, respectivelypon the followers "I8 and IQ forlimiting the 'outward'movementof the follower during the expansion orextension of the unit.

' It will be seen, by means of this arrangement,

that whether the unit is being compressed or expanded, there will befriction developed between the outersurface of the sleeve "28 and theexternal surface of the chambers, and that this friction will'besubstantially the same in either direction.

Suitable means area-lso provided for increasing this friction,and'in'the form of construction shown this is accomplished by providingone or more 'adrditional split sleeves which are adapted to nest "ortelescope within the sleeve 23. For the purpose of illustrating thisfeature of the invention, two additional sleeves 32 and 33 are employed.It'is evident that additional sleeves may be provided if it is necessaryto increase the capacity of the unit. Each of 'these interior sleeves,when normally expanded, has a greater diameter thanthe interior of thenext adjacent outer sleeve, 'sothat each must be compressed in order toplace the'same imposition within the adjacent outer sleeve. As a resultof this arrangement the additional sleeves tend to expand the outersleeve with a greater force, thereby creating greater friction betweenthe outer sleeve and the exterior chambers. In order that the expansionand compression of the sleeves shall be more uniform throughout theircircumference, the wall opposite the split, as at 30, is the thickestand gradually tapers toward the split.

Suitable means are provided for holding the sleeves fixed relative toeach other during the operation of the unit. 'Any suitable means may beemployed for locking the sleeves together, but in the form ofconstruction shown the sleeves are provided with ribs and correspondingrecesses which are adapted to engage each other for locking the sleevestogether. As shown, the outer sleeve is provided with a recess 34 onits'inner periphery, which is adapted to be engaged by a rib orcorrugation 35 formed in the sleeve 33. In forming this corrugation inthe sleeve 33 a corresponding groove or recess 36 is formed on itsinterior surface, which is adapted to be engaged by a, corrugation 31formed on the outer surface of the inner sleeve 32. In forming thiscorrugation a corresponding recess is formed on the inner sleeve whichis adapted to be engaged by a corrugation on the next size frictionsleeve, if it is desired to use the same. 7

In order to increase the capacity of the unit this may be done in twoways: one by increasing the capacity of the spring 22, and the other bythe use of additional resilient split sleeves which may be telescopedwithin the inner sleeve 32, as is obvious from an inspection of Fig. 3.Any required number of additional sleeves for increasing the frictionbetween the sleeve 28 and the inner surface of the followers I! and I8may be used, limited, however, by the ability of the spring to restorethe parts to normal position after release.

The unit is especially useful in preventing harmonic action of thespring assemblies of railway trucks. By adding or removing frictionsleeves the unit can be made adequate for preventing this harmonicaction in spring assemblies for cars of either low or high capacities;that is, the capacities of the unit maybe varied to meet varyingconditions.

It will be noted that the radially outward spring pressure exerted bythe sleeves 28, 32 and, 33 against the interior friction walls 23 of thetwo followers is constant at all degrees of expansion and contraction ofthe unit, and, moreover, that the areas in frictional contact areconstant throughout the range of compression and expansion. It isapparent then that the spring offers substantially constant frictionalresistance throughout its entire range of expansion and contraction.Unlike many spring units of this general type, the frictional resistanceof the present spring unit does not drop off sharply as the spring unitexpands to maximum length.

It is thought from the foregoing, taken in connection with theaccompanying drawings, that the construction and operation of my devicewill be apparent to those skilled in the art, and that changes in size,shape, proportion and detail may be made without departing from thespirit and scope of the appended claims.

I claim as my invention:

1. A bolster spring unit comprising a pair of opposed chamberedfollowers spaced apart, each follower having an outwardly extendingflange at its outer end and each having a cylindrical fric-' tionsurface, a spring between. said flanges, and

a plurality of expansible split sleeves extending between and into saidfollowers, each inner sleeve biasing the remaining sleeves radiallyoutwardly, the outer surface of the outer sleeve frictionally engagingthe interior walls of said followers.

2. In a device of the class described, a pair of chambered followersspaced apart and facing each other, each follower having a cylindricalfriction surface, a split friction sleeve normally of greater diameterthan the internal diameter of said chambers extending into said chambersand frictionally engaging said cylindrical surface, and

one or more split sleeves of resilient material telescoped Within saidfirst-named sleeve and biasing the latter radially outwardly, andresilient means for restoring the parts to normal position afterrelease. 7

3. A bolster friction spring unit comprising a pair of chamberedfollowers spaced apart each having an interior cylindrical frictionsurface, a onepiece expansible friction sleeve frictionally engagingboth said interior surfaces of said followers, a one-piece expansiblesleeve member engaging said friction sleeve for expanding the sameradially outwardly, and resilient means surrounding said chamberedfollower for expanding said unit after compression and release.

4. In a friction spring unit for use on railway equipment, a pair ofchambered followers each having a hollow portion having an innerfriction surface and a flanged portion, a spring surrounding said hollowportions and abutting against said fiangeathe interior of said hollowportions being enlarged in internal diameter at their outer end portionsto form shoulders, and an expansible friction one-piece split sleevefrictionally engag ing the interior walls of said chambers and havingoutwardly extending members for engaging said shoulders for limiting theexpansion of said unit.

5. In a bolster friction unit, a pair of openended followers facing eachother and spaced apart, said followers having cylindrical friction faceson their interior, a plurality of resilient telescoped members betweensaid followersand extending therein, the outer of said membersfrictionally engaging the interior friction surfaces of said followerssubstantially throughout their entire circumferences, each of saidtelescoped members having a greater unrestrained diameter than itsdiameter in the unit and tending to radially expand for frictionallyresisting the compression of said unit, and means for restoring theparts to normal position after release.

6. In a friction spring unit for use on railway equipment, a pair ofchambered followers each having a hollow portion having an innerfriction surface and a flanged portion, a spring surrounding said hollowportions and abutting against said flanges, and friction means includinga onepiece split sleeve member biased radially outwardly by its inherentresiliency and engaging the friction surfaces at the inner ends of saidfollowers substantially throughout the entire inner circumferencethereof.

7. A bolster friction spring unit comprising a pair of chamberedfollowers spaced apart each 8. In a bolster unit for acting withsubstantially uniform frictional resistance throughout its range ofmovement between maximum extension and maximum compression, a pair ofchambered followers each having a cylindrical frictional surface ofuniform inner diameter, a helical spring acting in compression betweensaid followers to expand the unit, means to limit the expansion of theunit by said helical spring, and a pring in the form of a sleeve with asingle split with two adjacent edges, said last named spring being ofreater unrestrained diameter than the inner diameter of said frictionalsurfaces and being confined within the diameter of said surfaces forcontinuously exerting outward radial pressure against said surfaces, thelongitudinal extent of the areas of contact between each of the twofollowers and the areas of said last named spring on opposite sides ofthe split therein being substantially equal, thereby avoiding anymaterial tendency for said last named spring to be expanded byunbalanced longitudinal forces.

HERBERT E. TUCKER.

REFERENCES CITED The following references are of record in the file ofthis patent:

